Titanium Silicide Formation and Arsenic Dopant Behavior under Rapid Thermal Treatments in Vacuum

Abstract

Titanium thin films were deposited by RF sputtering on lightly and heavily arsenic‐implanted silicon wafers. These wafers were treated by means of a rapid thermal graphite heater in vacuum for different times and temperatures. The silicide formation and the arsenic behavior, in the substrate, are studied by means of XRD, AES, RBS, and four‐point probe measurements. At the initial stage a high concentration of oxygen and carbon is incorporated in the film and a titanium rich silicide is formed. For longer times and intermediate temperatures (550°–700°C) a three‐layer film is formed: . By increasing temperature, in the same range, the layer grows thicker, and its formation results in the repulsion of oxygen and carbon. Meanwhile, the titanium‐rich silicide vanishes. At higher temperature (800°C) the phase is obtained promptly after the initial stage. Arsenic presents an inhibition effect on silicide formation at the intermediate temperature range and seems to ease the transformation from to phase. An arsenic snowplow effect is observed for short treatments at 800°C and an increasing arsenic loss is observed with increasing time and temperature. A higher final arsenic concentration in the substrate is observed for formed by a two‐step treatment, as in the Salicide process, compared with a single treatment at high temperature (800°C).